The highly addictive mix of marijuana, tentanyl and tramadol has caused hundreds of deaths and psychiatrically damaged scores of users since it first appeared in Sierra Leone around four years ago, according to the government. There are no official figures on the exact number of deaths.

Bio announced the national emergency in a late night address on Thursday, deploring what he said were "the destructive consequences of kush on our country's very foundation: our young people".

He said a national task force on substance abuse - involving all sectors of society and supervised by a presidential advisory team - would be set up to implement a five-step strategy for what he called a drug-free future.

Kush's low price makes it accessible to disillusioned, unemployed youth in Sierra Leone, where around a quarter of the population lives in poverty. The drug is also found in the neighbouring West African nation of Liberia.

Local communities have called on the government to tackle the scourge and help them deal with drug users.

The head of Sierra Leone's only psychiatric hospital, Abdul Jalloh, welcomed Bio's declaration as a crucial step towards addressing drug use.

(Reporting by Umaru Fofana; Editing by Sofia Christensen and Frances Kerry)